Mrs. NFC and I were just in Munich and we had a wonderful time. It's a great city. Your kids are so lucky. If they haven't traveled overseas before, this will be an amazing first international trip.

The suggestions made throughout the thread are right on. Here are a couple of links that we used to prepare for our trip:

Lonely Planet - Munich
Munich's Official Site

Also, here are a couple of kids oriented links:
Frommers - Munich for Kids
Travel for Kids

Enjoy!